IEEE (Institute of Electrical and Electronics Engineers) 802.16 standard provides techniques and protocols for supporting broadband wireless access. The standardization had been conducted since 1999 until the IEEE 802.16-2001 was approved in 2001. The IEEE 802.16-2001 is based on a physical layer of one carrier (SC) called ‘WirelessMAN-SC’. The IEEE 802.16a standard was approved in 2003. In the IEEE 802.16a standard, ‘WirelessMAN-OFDM’ and ‘WirelessMAN-OFDMA’ are further added to the physical layer in addition to the ‘WirelessMAN-SC’. After completion of the IEEE 802.16a standard, the revised IEEE 802.16-2004 standard was approved in 2004. To correct bugs and errors of the IEEE 802.16-2004 standard, the IEEE 802.16-2004/Cor1 was completed in 2005 in a format of ‘corrigendum’. A standard based on IEEE 802.16-2004/Cor1 is referred to as IEEE 802.16e or WiMAX.
Recently, IEEE 802.16 broadband wireless access working group has standardized a new technical standard IEEE 802.16m based on IEEE 802.16e. The newly developed IEEE 802.16m should be designed such that it can support the previously designed IEEE 802.16e. That is, the newly designed system IEEE 802.16m shall be composed to operate under efficiently covering the existing system IEEE 802.16e. This is referred to as backward compatibility.
Techniques of improving reliability of wireless communication include ARQ (Automatic Repeat Request). The ARQ allows a transmitter to retransmit a data signal when a receiver fails in receiving the data signal. Furthermore, there is HARQ (Hybrid Automatic Repeat Request) corresponding to a combination of FEC (Forward Error Correction) and ARQ. A receiver using HARQ attempts error correction on a received data signal and determines whether the data signal is retransmitted using an error detection code. The error detection code may use CRC (Cyclic Redundancy Check). The receiver determines that the data signal has been successfully decoded when any error in the data signal is not detected through a CRC detection process. In this case, the receiver transmits an ACK (Acknowledgement) signal to a transmitter. The receiver determines that the data signal has not been decoded when an error in the data signal is detected through the CRC detection process. In this case, the receiver transmits a NACK (Not-acknowledgement) signal to the transmitter.
As described above, the HARQ is an important technique for improving the reliability of wireless communication. To perform HARQ, the time when a data signal is transmitted or received and the time when a HARQ ACK/NACK signal with respect to the data signal is transmitted or received are important issues. Accordingly, there is a need for a method of efficiently performing HARQ in a wireless communication system.